1. Field of the Invention
The present invention relates to chargers for use with battery packs which are used to run electric power tools. More particularly, the present invention relates to a battery pack charger with an improved mechanism for protecting its terminals.
2. Description of the Related Art
One type of known battery charger includes a connecting portion, such as a pair of guide rails protruding therefrom on which a battery pack is set for charging. A battery pack to be charged by such a charger typically includes a pair of slide rails provided on the surface of the battery pack that is set on the charger during a charge. The slide rails can be engaged with and slid along the guide rails of the charger in order to removably set the pack in place on the charger. When the battery pack is attached to the charger by sliding of the pack's slide rails along the charger's guide rails, electrical contact is established between the charge terminals and communication terminals provided on the connecting portion of the charger and the charge/discharge terminals and communication terminal of the battery pack.
While this type of battery charger achieves its intended objective, it is not free from certain problems and inconveniences, thus leaving room for improvement. For example, as the terminals of a charger of this type are exposed at the connecting portion to the external environment when the battery pack is not attached to the charger, the terminals may break or otherwise suffer damage that may result, for example, from the charger dropping to the floor or, conversely, by an object falling onto the charger. In view of such problems, Japan Published Unexamined Patent Application No. 2001-128372 proposes a charger that includes a terminal cover in a connecting portion where a battery pack is attached. According to the disclosure, the terminal cover is adapted to cover the charger terminals when the battery pack is not attached to the connecting portion and to be actuated by a motion of attaching the battery pack to the connecting portion to expose the charger terminals when the pack is attached to the connecting portion.
While this improved arrangement achieves its intended objective, it still suffers from certain deficiencies that reduce the utility of the device. For example, the terminal cover of the aforementioned disclosure is adapted to rotate between a protruding position, in which the cover protrudes from the housing and the connection portion so as to cover the charger terminals from the front of the charger, and a retracted position, in which the cover is retracted inside the housing in the direction of the slide of the battery pack so as to expose the charger terminals. This particular arrangement requires a through-hole in the charger housing so as to permit the protrusion and retraction of the terminal cover. Depending on the working environment, such as in outdoor environments, this arrangement is susceptible to ingression of rain, dust, and other foreign matter through the through-hole, thereby causing short-circuiting or other such failures.
Another disadvantage associated with the foregoing device is the need to allocate or reserve the space within the housing to allow the terminal cover to be retracted inside the charger. This results in otherwise unnecessary increases in the size of the entire device.